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The effects of spinal manipulation therapy on migraine are likely due to the placebo effect.

Note that the study only examined manipulation therapy, and not the other interventions that may come along with it such as other manual and nonmanual interventions.

The effects of spinal manipulation therapy on migraine are likely due to the placebo effect, according to the first randomized, sham-controlled trial to investigate the question.

Three groups -- an intervention group, a sham manipulation group, and a "placebo" group on regular medical management -- had a similar reduction in migraine days at the end of the 3-month study, Aleksander Chaibi, a physiotherapist and chiropractor and a PhD candidate at Akershus University Hospital in Norway, and colleagues reported online in the European Journal of Neurology.

Those reductions held at 1 year for patients in the real and sham manipulation groups, but returned to baseline in the medical management group, suggesting that the effect of chiropractic spinal manipulation therapy "is probably due to a placebo response," they wrote.

There are several reasons that it's been a challenge to have a randomized controlled trial of manipulation therapy, the researchers said. First, the therapist can't be blinded, and second, there hasn't been a proper sham procedure.

Chaibi and colleagues aimed to address the latter half of those challenges by developing a procedure where migraine patients couldn't distinguish between real and sham manipulation therapy. It involved a sham push maneuver of the lateral edge of the scapula and the gluteal region.

"We acknowledge that our placebo intervention could be criticized for giving some physiological effect because the palpatory procedures and the placebo contacts elicited an afferent neurological response, as every manual contact will do, including a simple hand shake," Chaibi told MedPage Today. "However, we do not believe that our placebo sham intervention by itself had any effect other than a placebo effect, particularly considering that all the placebo contacts were pre-defined and made outside the spinal column."

They randomized 104 migraineurs to either that sham procedure, actual manipulation therapy, or to a control that was comprised of usual pharmacologic management. The manipulation therapy involved the Gonstead method, a specific contact, high-velocity, low-amplitude, short-lever spinal push with no post-adjustment recoil that was directed at spinal biomechanical dysfunction.

Both the sham and the intervention were 15 minutes long, and both groups had the same structural and motion assessments prior to and after each intervention. Participants didn't receive and other intervention or advice during the trial, and all kept a headache diary.

The primary endpoint was the number of migraine days per month, measured at 3 months.

Overall, they found similar, significant reductions in migraine days from baseline across all three groups at 3 months (P<0.001), and those reductions were not statistically significant between groups.

That effect continued in the manipulation therapy and sham groups at all follow-up time points, including 6 and 12 months, whereas the control group returned to baseline levels at 1 year, the researchers reported. At that point, the active intervention group improved by about 40% compared with the control group of usual care with pharmacologic management, Chaibi said.

The researchers did see a significant reduction from baseline in migraine duration, intensity, and headache index in both the manipulation therapy and sham treatment groups at 3, 6, and 12 months.

Blinding appeared to be satisfactory: After each of the 12 intervention sessions, more than 80% of the participants believed they had received manipulation therapy regardless of group allocation, they reported.

Adverse events were few, mild, and transient, and they occurred significantly more frequently in the manipulation therapy group, the researchers said.

Chaibi noted that 15% of migraineurs don't respond to pharmacologic management with NSAIDs or triptans. He also noted that medication overuse as a result of frequent migraine attacks is a concern. These are areas where chiropractic care -- even if the result of a placebo effect -- may have application, he said.

"Considering that this profession has a 5-year master university degree, it goes without saying that this profession holds the theoretical competency to handle patients who do not respond to pharmacological management, either through direct manual management, or better, in combination with information and general advice," Chaibi said.

He noted that the study only examined manipulation therapy, and not the other interventions that may come along with it: "Chiropractic care ... is [typically] bound with other manual and non-manual interventions, such as soft tissue techniques, spinal and peripheral mobilization, rehabilitation, postural corrections and exercises, general nutrition and dietetic advice, and other general lifestyle advice," he said. "Including additional approaches, especially advice and information in clinical practice, would probably further improve these patients."

Chaibi noted that the study included patients from secondary and tertiary care centers, so the results may not be generalizable to the primary care population, which chiropractors tend to be involved in.

Richard Lipton, MD, of the Montefiore Headache Center in New York, who wasn't involved in the study, said the inclusion of both a sham arm and a "placebo" medical management was a strength of the study.

"Both real and sham [manipulation therapy] are associated in reduction in headache days relative to the usual care arm," Lipton told MedPage Today. "Because real and sham [manipulation therapy] are equally effective, that supports one of two conclusions. One possibility is that the apparent benefits of manipulation therapy are placebo effects, induced by the laying on of hands."

"The other possibility is that both real and sham manipulation therapy are effective treatments," he continued. "The fact that the treatments had very favorable safety results is reassuring. Based on these results, manipulation therapy is not an evidence-based therapy. Given the benefits relative to usual care and its safety, it may be worth a try in people whose treatment needs are not met by usual, evidence-based treatments."

The authors disclosed no financial relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner